(1) Field of the Invention
This invention relates to a filter mounted at a free end of a suction pipe of a liquid suction device.
(2) Description of the Prior Art
A filter is mounted at the suction pipe of a fuel tank for an internal combustion engine or a lubricant tank for a small machine of a portable type to prevent the entry of dust or other foreign matter into the suction pipe. Proposals have been made to use elastic material to form such suction pipe to enable all the liquid in the tank to be drawn by the suction pipe regardless of the posture of the machine.
A filter having an elongated cylindrical form has usually been used and has suffered the disadvantages that the finish and the shape of its filter element do not lend themselves to easy treatment, resulting in the filter becoming high in cost in spite of its size being small. To obviate this problem, proposals have been made to use a swingable filter of spherical shape, as disclosed in Japanese Utility Model Examined Publication No. 42096/84 (corresponding to U.S. Pat. No. 4,428,835 too Nagashima), for example. This type of filter is simple in construction, low in cost and capable of cleaning itself by its swinging movement during operation. It is earnestly desired nowadays that further improvements be incorporated in the construction of the filter to provide improved filtering function.